1. Field of the Invention
The present invention relates to controls for controlling engine fueling in a vehicular automated mechanical transmission system. In particular, the present invention relates to controls for automatically controlling the fueling of non-electronically controlled engines in automated mechanical transmission systems during both upshifting and downshifting, which provides improved shift quality, and which will not cause unintended full fueling of the engine with the driveline engaged as the result of a single point failure arid will quickly respond to certain multiple point failures leading to undesired increased engine fueling by returning fuel control to the vehicle operator.
2. Description of the Prior Art
Automated mechanical transmission systems and controls therefor are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,595,986; 4,614,126; 4,648,290; 5,063,511; 5,109,729; 5,117,791 and 5,335,566, the disclosures of which are incorporated herein by reference.
In automated mechanical transmission systems equipped with electronically controlled engines (i.e., engines having dedicated microprocessor controllers and communicating with a data bus, such as the data buses conforming to the SAE J-1922 or SAE J-1939 protocols), engine fueling during both upshift and downshift transients typically is controlled by a system controller which causes fuel "dip" (Le., decreased fueling) or fuel "blip" (Le., increased fueling), as required, regardless of the operators positioning of the throttle pedal.
In systems with electronically controlled engines, the driver's throttle position is one of multiple inputs to a controller, which issues command output signals to various actuators, including the engine fuel controller (see, for example, U.S. Pat. No. 5,425,284, the disclosure of which is incorporated herein by reference). The controller usually communicates with the engine fuel control over an electronic data link or data bus of the type conforming to a standardized protocol such as SAE J-1922, SAE J-1939 or ISO 11898. In systems with non-electronically controlled engines, the operator's throttle setting is a direct input to the engine fuel controller, which input may be interrupted or modified by various devices.
In vehicles not equipped with electronically controlled engines, automatic throttle dip was used to break torque across engaged jaw clutches for shifting into neutral and to synchronize for upshifts. However, automatic throttle blip was not used during downshift transients to prevent the possible occurrence of a single point failure resulting in the dangerous condition of continuous unintended increased fueling of the engine, especially in conditions of an engaged drivetrain (i.e., master clutch engaged and transmission not in neutral). Such systems typically required manual synchronizing (i.e., increased engine and input shaft speeds) for downshifts and/or used power synchronizer devices (see aforementioned U.S. Pat. Nos. 4,614,126 and 5,063,511) and/or required elaborate redundant safety features.
The prior art automated mechanical transmission systems not utilizing electronically controlled engines were subject to improvement in the areas of control complexity and/or shift rapidity and quality.